All pretreatments were conducted at 20% solids content by mixing
400 g dry biomass with 1.6 l tap water or dilute acid. Five hot
water pretreatment conditions were chosen at temperatures of
160–200 C and operation times of 4–8 min. Detailed pretreatment
conditions for hot water are summarized in Table 1. Dilute acid
pretreatment conditions were modified from previous reports,
S.M. Kim et al. / Bioresource Technology 216 (2016) 706–713 707
stating that high sugar yields were achieved with a combined
severity factor (cSF) of 1.5 (Lloyd and Wyman, 2005; Schell et al.,
2003). Here, cSF values of 1.46 and 1.01 were chosen as high and
mild dilute acid severities to compare to hot water pretreatment
alone. Corn stover was pretreated at 150 C for 4 min with 1.0%
w/w sulfuric acid (DA, 1.0% at 150 C for 4 min) for cSF 1.46 and
at 160 C for 4 min with 0.55% w/w sulfuric acid (DA, 0.55% at
160 C for 4 min) for cSF 1.01. Pretreated sample pH was measured
and heating and cooling temperatures were recorded every 5 min.
Pretreatments were performed one time at a given condition due
to the large amount of samples used.